1. Field of the Invention
The present invention relates to a fiber-containing peelable solvent-based coating remover that may be applied to a wide variety of coatings and substrates and which can be easily removed by peeling and without more than about 10-20%, preferably, substantial, readhesion of the removed coating to the originally coated surface. Coating removers of the present invention can cling to the underside of a horizontal substrate, such as an overhead surface, or to a vertical substrate, without substantially dripping away therefrom.
2. Description of Related Art
Protective or decorative coatings such as paint, paint primers, varnish and other natural or synthetic coatings are applied to a wide range of substrates including metal, wood, artificial wood surfaces, brick, glass and concrete. When a coating deteriorates or when a new coating is desired for aesthetic reasons, the original coating frequently must be removed before a new coating is applied.
Development of new synthetic coating materials has created a need for more versatile coating removers that are effective in removing the wide range of new synthetic coatings and which will not harm the substrates. Moreover, increased awareness of the harmful effects of prolonged exposure to wet, volatile solvents has increased the need for safer solvent-based systems.
There are two principal kinds of coating removers, caustic alkali systems and solvent-based systems. Early coating removers typically used alkalies such as caustic soda, potash and soda ash as the primary ingredient. Alkali systems sometimes included other ingredients such as mineral spirits, turpentine and benzene. These alkali coating removers did an adequate job in removing natural shellacs, varnishes and resins. Their ability to remove modern synthetic coatings, however, is inferior and caustic alkali solutions frequently damage substrates to which the coatings are applied. For instance, caustic alkali formulations have been known to stain wood substrates, degrade fibrous material in substrates and etch metal substrates.
To overcome some of these disadvantages, cloth-caustic alkali systems were developed in which liquid caustic soda is painted directly onto a coating to be removed and a cloth is placed over the caustic soda solution. After standing overnight, the dried caustic and coating are removed by removing the cloth from the surface. Under proper conditions, the coating sticks to the cloth and is removed without damage to the substrate.
The utility of this system is limited, however, since it can only be used on a relatively small number of coatings attacked by caustic formulations and only a few square feet of substrate can be treated at one time. Treating larger areas is impractical due to the time and expense involved in using cloth for one area and then cleaning the cloth for use on a different area. Large cloths, of course, would be difficult to use and clean.
An improvement on the caustic system is disclosed in U.S. Pat. No. 4,502,891 which describes aqueous solutions of caustic coating remover which include caustic, chalk and natural or synthetic fibers. The aqueous product dries to a peelable coating and the paint is removed in dry form. The disadvantage of this system, like the cloth-caustic system, is that it is limited to attacking only certain coatings and frequently may damage the substrate. Accordingly, caustic systems are not sufficiently versatile for removing a wide variety of modern synthetic coatings and continue to cause damage to substrates. They also do not cling well to overhead or vertical surfaces, thereby impairing their effectiveness for removing coatings from overhead and vertical surfaces.
The disadvantages of solvent-based removers are well-known to those who routinely use such products. Conventional solvent-based coating removers are typically less effective on vertical andoverhead surfaces such as ceilings and walls than on surfaces which support the coating remover, such as floors, because conventional coating removers often drip away from vertical and overhead surfaces in amounts sufficient to impair their effectiveness.
In an attempt to solve these problems, viscosity builders have been added to solvent-based formulations, but the ability of these formulations to cling to vertical and overhead surfaces remains inadequate. Typically, for instance, an amount of about 50% of conventional solvent-based coating removers may drip away from overhead surfaces, thereby reducing the amount of solvent available to remove the coating. The amount which drips away, of course, also depends on other factors such as the thickness of the coating remover applied to an overhead or vertical surface.
Usually, a solvent-based paint remover is spread onto a coated substrate in one direction with a paint brush or roller. Sufficient time is then allowed to permit the solvents to loosen the coating from the substrate surface. With conventional solvent-based coating removers, some deposed coating typically readheres to the substrate if the remover is left on the substrate and coating for too long a time. Accordingly, conventional coatings are ordinarily removed while still wet since allowing them to dry results in undesirable readhesion of the coating to the substrate. Ordinarily, therefore, the coating and coating remover are scraped away from the substrate as a slushy mixture or washed away from the substrate with a solvent or water. Workers are necessarily exposed to the solvent vapors of conventional coating removers which are not allowed to dry.
Prolonged exposure to the solvents in a solvent-based system may irritate a worker's eyes, skin and lungs. Even in good ventilation, workers in a limited space with wet solvents for extended periods of time may be exposed excessively to solvent vapor fumes. To minimize exposure of workers to solvent fumes, only small areas of a job may be done at a time.
Exposure is also encountered when the worker is scraping the slushy mixture of the coating and remover from the substrate. When removing coatings from overhead or vertical surfaces, eye and skin contact must be carefully guarded against by wearing protective clothing and masks to prevent contact of the wet active solvents.
Moreover, once a worker has applied a coating remover, he must observe the remover from time to time to make sure that excessive evaporation does not occur. Excessive solvent evaporation may lead to readhesion of the coating to the surface thereby defeating the efforts to remove the coating. The constant need to oberve the work surface and the need to limit a worker's exposure to the solvents in a given period of time increases the labor cost of coating removal.
Mixtures of solvent-based coating removers and removed coatings often take days to dry when large amounts of these wastes are collected together. In addition to the problems associated with exposing workers to the fumes from these wet solvents and coatings, disposal of the solvents into a sewer is prohibited by many cities and states for environmental reasons. Wet mixtures of coating removers and coatings must therefore be stored in special containers and delivered to an approved company for disposal.
To overcome some of the drawbacks of solvent-based coating removers, attempts have been made to formulate a solvent system with an inorganic powder. The solvent-based remover is combined with the powder applied to the coating and allowed to dry overnight. The dried coating remover and coating must then be scraped from the surface. The removed coating, for instance, paint, adheres to the inorganic powder and can be scraped from the surface of the substrate in dried form.
The dried powder, however, often adheres to the substrate that the coating was applied to. This requires additional scraping which increases the number of scrape marks and may also damage the substrate. This disadvantage limits the utility of the powder formulations in applications such as fine furniture, particularly furniture with curved surfaces.
Furthermore, the dried powdered method is not satisfactory for removing material from overhead and vertical surfaces since the dried material comes off as a powder which remains in the ambient air. Therefore, when the dried coating and powder are scraped off, the powder may enter the worker's eyes or respiratory system.
The present invention provides a solvent-based coating remover with a number of improved properties. Solvent-based coating removers made in accordance with the present invention can dry to form a peelable combination of deposed coating, fibers and binder without permitting more than about 10-20% of the deposed coating to readhere to the substrate from which the deposed coating is removed.
Coating removers of the present invention can cling to the underside of a horizontal substrate or to a vertical substrate substantially without dripping away from the overhead or vertical surface when applied in an amount sufficient to depose the coating. The present invention also provides a coating remover with improved clinging characteristics and which typically has from at least about 10% to 300% less material drip away from overhead and vertical surfaces than conventional coating removers. Coating removers of the present invention are also easier than conventional coating removers to remove from substrates.
Specifically, the coating being removed and the coating remover of the present invention can be removed with less damage to the substrate than has been possible with conventional coating removers. Moreover, coating removers of the present invention can be more effective than conventional coating removers on a larger variety of substrates and can be easier to dispose of after use.